Recently, a pedestrian-protecting airbag system for a vehicle is developed to protect a pedestrian. When the vehicle collides with the pedestrian, the pedestrian-protecting airbag system provides an airbag which is deployed on a bonnet of the vehicle to prevent a head portion and a breast portion of the pedestrian from colliding with the bonnet or a windshield of the vehicle.
Thus, a collision obstacle discrimination device becomes necessary for an actuation of the pedestrian-protecting airbag system. That is, it is necessary for the collision obstacle discrimination device to real-time discriminate between a pedestrian who is to be protected by the deployed airbag and other objects which are unnecessarily protected. In the case where the pedestrian-protecting airbag is unnecessarily deployed, an extra repair cost is to be spent. Moreover, the collision obstacle discrimination device is required to have a quick response performance, because the pedestrian-protecting airbag is to be deployed earlier than the violent collision of the pedestrian with the vehicle.
Referring to U.S. Pat. No. 6,784,792-B2, for example, each of the bonnet and a bumper of the vehicle is provided with a collision detection sensor, to judge whether or not the obstacle is a pedestrian based on outputs of the sensors.
In this case, the single sensor is attached to the bonnet so that the collision obstacle cannot be sort-distinguished until colliding with the bonnet. That is, the quick response performance of the discrimination device referring to JP-2003-535769A is inferior. Thus, when the obstacle is a pedestrian, it is difficult to deploy the pedestrian-protecting airbag to protect the pedestrian before the pedestrian violently collides with the bonnet. Furthermore, because the collision detection sensor is attached to the bonnet, the obstacle having a total height smaller than that of the bonnet cannot be substantially sort-distinguished.